Conventionally, this kind of large deck vessel with multi-legs has been known by a Japanese examined patent publication No. TOKUKQHEI 7-100466, which was invented by the inventor of the present invention.
In the large deck vessel with multi-legs, the vessel is intended to have such a large deck that the width or length of the deck is from tens of meters to thousands of meters or more. As for the purpose of the vessel, the vessel is intended for use not only as a transport ship having a large transportation capacity in place of a conventional giant tanker, but also as a solar energy ship, a moving airport, or a sea farming mother ship using the large deck. Furthermore, making use of the characteristic that the submerged body is kept cool by the surrounding water which is at almost a constant temperature throughout the year, any one of an economical special refrigerated ship, a chemical transport ship, or an LNG long-distance transport ship can also be an intended use of the vessel.
The large deck vessel with multi-legs has a special structure, made up of an upper body which is always above water, a submerged body which is always submerged under water and disposed under the upper body, and a plurality of legs which connect the upper body and the submerged body. The large deck vessel with multi-legs has various kinds of special characteristics different from a conventional ship because of the special structure of the large deck vessel according to the present invention.
For instance, the upper body is influenced by the heat caused by sunlight and by the wind in a different level or manner in comparison to a conventional ship, because the upper body forming a deck in the large deck vessel of the present invention is always positioned above water. In the case of the large deck vessel having an upper body which forms an especially large deck, since the influence of wind to the upper body is significant, the larger the deck, i.e., the upper body, the larger the power needed for lifting, lowering, or inclining the upper body becomes. Furthermore, the larger the surface area of the deck exposed to sunlight or cold wind, the larger the influence caused by thermal expansion or contraction of the upper body becomes.
Although the submerged body is always under water and therefore is not influenced by the wind, the submerged body is heavily influenced by the resistance of water when the vessel begins to incline or restore itself to its original posture. For example, in the case of a conventional ship, sea waves affect large changes in the buoyancy of the whole ship because they directly act against the ship. In the case of the large deck vessel with multi-legs, however, sea waves affect only the connecting legs because the upper body is completely above water and the submerged body is always under water. Further, the total volume of the legs is very small compared to the total volume of the submerged bodies, and the different phases of the sea waves encountering the connecting legs will be set off by one another because of the dispersedly disposed connecting legs. As a result, changes in the buoyancy of the whole vessel due to the sea waves are considerably smaller than the changes in buoyancy of a conventional ship.
Furthermore, the large deck vessel with multi-legs has the special characteristic that a longer time is needed to restore the vessel from an inclined state to an upright state than the restoring time needed for a conventional ship. In other words, when the vessel is inclining, a vertical downward gravity of the vessel at the center of gravity of the ship, a vertical upward buoyancy of the vessel at the center of the buoyancy of the vessel, and a resistance power for displacing water by the submerged bodies brought about from when the vessel starts inclining until it stops inclining, will act as righting moments. However, there is the drawback that a longer restoring time is needed because the resistance power also acts as an anti-righting moment when the vessel starts restoring from the inclined state toward the upright state since the resistance power acts in a direction opposite to the restoring direction.
As mentioned above, in the large deck vessel with multi-legs, the vessel has a special constitution different from a conventional ship. The vessel is heavily influenced by the wind because it has an upper body constituting a large deck. The vessel should be designed with thermal influence caused by the sunshine and cold wind taken into consideration. Furthermore, the upper body, constituting a large deck, is required to maintain a correct posture at all times in spite of the changing position of the center of gravity due to loading, unloading or moving a cargo or similar.